Gas-filled discharge tube



Jan. 26, 1937.

H. H. GEFFCKEN ET AL ,741

GAS-FILLED DISCHARGE TUBE Filed NOV. 9, 1934 INVENTOR flemmw H. GEFFCKENAND HANS RRKHTER ATTORNEY Patented .lan. 26,- 1937 UNITED STATES PATENTOFFICE GAS-FILLED DISCHARGE TUBE Application November 9, 1934, SerialNo. 752,214

In Germany November 11, 1933 4 Claims. (Cl. 176-122) Our inventionrelates to gasfilled discharge tubes of the kind comprising a sealedglass bulb, filled with rarefied gas (especially neon) and having onefused and one capacitively acting condenser electrode. Tubes of thiskind are especially manufactured in miniature dimensions and used forindicating and signalling purposes. In consequence of the dielectricresistance of the condenser electrode, such tubes can be used withalternating current without any series resistance.

In manufacturing such tubes under exactly comparable circumstances wehave found, that the discharge potential varies in a disturbing manner,this being an especially serious drawback if the tubes are used undernormal network voltages, such as for indicating open switches.

Our invention relates to tubes of the described kind, which are free ofsuch drawbacks and which have a very low and constant discharge.potential practically not differing one from another. Furthermore ournew tubes give a relatively intense and well concentrated light whichmay be discerned from a distance of several meters, even if the tubecurrent is below 0,1 m. a. The essential feature of our novel tubesconsists in extending the electric conducting foil or layer, used as acondenser electrode, over the whole wall of the bulb except a littlewindow and except the indispensable insulating spaces. Preferably thefront of the tube is used as a window while the condenser electrode foilcovers the entire cylindrical portions of the tube except the portionsnear the fusing point of the inner electrode.

Our invention will best be understood by de- 3 tailed description withreference to the accompanying single sheet of drawing in which.

I Figures 1 and 2 represent known types of discharge tubes, which showthe beforesaid drawbacks.

Figures 3-5 represent schematically the crosssections of three difierentembodiments of our invention.

Figure 6 shows another embodiment of our invention and 45 Figure 7 showsa switch, equipped with a tube according to our invention.

Referring now to Figs. 1 and 2 the tube I contains an inner electrode 2sealed in at 3 and an outer capacitative electrode, represented by thefoil 4 which may consist of metal foil or a metallic layer sprayed ontothe surface of the tube'or the like. In Fig. 1 the condenser electrodeis formed in the manner of a cap; in Fig. 2 said electrode has anadditional tongue 5 for 55 increasing its capacity. The tube I is filledwith rarefied gas, preferably with neon, helium, argon or a mixture ofthese gases at a pressure of about 5-30 mm. Hg. In use, the electrodes 2and 4 are connected to the power line and the tube is viewed indirection of the arrows 6. As aforesaid'great irregularities take placein the discharge potential of such tubes and we have found, that theseirregularities are produced by uncontrolled electric charges on theintermediate parts of the walls of the vessel, said charges- 10schematically'marked by the points l-acting in the manner of the grid ina grid-glow-tube, andbeing able to enormously increase the dischargepotential.

The remaining Figures 3-5 represent some tube 15 constructions,according to our invention and which are characterized by the lack ofany free portions of the glass walls in the neighborhood of the pathwhere the discharge is started not covered by the outer metalliccoating. The vessel 8 is filled with rarefied gas in the usual mannerand sealed at 9. The inner electrode Ill consists of a straight wire,arranged concentrically in the tube 8 and sealed in at I l. Thecondenser electrode l2 covers the entire cylindrical portion of the tubeexcept the insulation space I 3. The front of the tube serves as awindow and the discharge layer M is viewed thru the window in thedirection of the arrows l5. In this manner the viewing direction isalong the lengthwise dimensions of the layer resulting in a relativelyhigh light intensity per unit area and a correspondingly goodvisibility.

In Fig. 4 the diameter of the tube is reduced on the front in order tosimplify the mounting of the tube. In Fig. 5 the front of .the tube isspherical and the wire electrode It] bears a spiral head l6, thusincreasing the lateral visibility of the glow; in order to concentratethe discharge, the lower end of the wire I0 is protected by a tubularglass envelope or sleeve H.

The condenser electrode l2 consists preferably of a sprayed on metalcoating; in some cases also a metal tube (preferably of splitconstruction) may be used. Fig. 6 shows a discharge tube, constructedaccording to our invention and fitted in the wall ll! of a housing orthe like. A slit metal tube I 9 is molded in said body l8 and the tube 8is pushed upward into the metal tube until its constricted front portionhas passed the 5 opening 20. In use the metal tube l9 and the electrodeID are connected to the power lines.

According to Fig. '7 the body 2| contains the tube 22 and two contactelements 23, 24. The tube is mounted to the switch 25 by means of thecommon base plate 26. The body 2| serves as an additional electricaldevice, which may be used in combination with any known type of switch.The tube 22 is connected in parallel to the switch 25 and thereforelights up when. the contacts of the switch are open and is extinguishedwhen the contacts are closed as is well understood. By

' these means the switch is made visible in dark rooms and can easily tobe found. The current consumption of the tube 22 is negligible.

Having now described our invention, what we claim is:-- v

1. A luminous glow discharge tube comprising a cylindrical envelope, agaseous atmosphere therein, a first co-axial wire shaped electrodemounted within said envelope and extending close to the front endthereof, and a second concentric electrode covering the outer wall ofsaid envelope to such an extent as to be equidistant from said firstelectrode throughout substantially the entire length of the latter.

2. A luminous glow discharge tube comprising a cylindrical insulatingenvelope, a gaseous atmosphere therein, a first co-axial wire shapedelectrode mounted within said envelope and extending close to the frontend thereof, and a second electrode constituted by a coating ofconductive material applied to the outer wall of said envelope to suchan extent as to be equidistant from said first electrode throughout theentire V effective length of the latter.

3. A luminous glow discharge tube comprising a cylindrical insulatingenvelope, a gaseous atmosphere therein, a first co-axial wire shapedelectrode mounted within said envelope, and a second electrode coveringsubstantially the entire outer surface of said envelope except for itsend portions to provide mounting space and leave a viewing window, saidfirst electrode extending close to said window.

4. A luminous glow discharge tube comprising a cylindrical insulating.envelope, a gaseous atmosphere therein, ,a' first co-axial wire shapedelectrode mounted 'within said envelope, and a second electrodeconstituted by a conductive coating applied to substantially the entireouter wall of said envelope except for its end portions to providemounting space and leave a viewing window, said first electrodeextending throughout the entire length of said envelope and close tosaid window.

HEINRICH H. GEFFCKEN. HANS R. RICH'I'ER.

